@ ProgramNode (location: (1,0)-(5,45))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(5,45))
    └── body: (length: 3)
        ├── @ DefNode (location: (1,0)-(1,39))
        │   ├── name: :m
        │   ├── name_loc: (1,4)-(1,5) = "m"
        │   ├── receiver: ∅
        │   ├── parameters: ∅
        │   ├── body:
        │   │   @ StatementsNode (location: (1,7)-(1,34))
        │   │   └── body: (length: 1)
        │   │       └── @ SingletonClassNode (location: (1,7)-(1,34))
        │   │           ├── locals: []
        │   │           ├── class_keyword_loc: (1,7)-(1,12) = "class"
        │   │           ├── operator_loc: (1,13)-(1,15) = "<<"
        │   │           ├── expression:
        │   │           │   @ SelfNode (location: (1,16)-(1,20))
        │   │           ├── body:
        │   │           │   @ StatementsNode (location: (1,22)-(1,29))
        │   │           │   └── body: (length: 1)
        │   │           │       └── @ ConstantWriteNode (location: (1,22)-(1,29))
        │   │           │           ├── name: :A
        │   │           │           ├── name_loc: (1,22)-(1,23) = "A"
        │   │           │           ├── value:
        │   │           │           │   @ NilNode (location: (1,26)-(1,29))
        │   │           │           └── operator_loc: (1,24)-(1,25) = "="
        │   │           └── end_keyword_loc: (1,31)-(1,34) = "end"
        │   ├── locals: []
        │   ├── def_keyword_loc: (1,0)-(1,3) = "def"
        │   ├── operator_loc: ∅
        │   ├── lparen_loc: ∅
        │   ├── rparen_loc: ∅
        │   ├── equal_loc: ∅
        │   └── end_keyword_loc: (1,36)-(1,39) = "end"
        ├── @ DefNode (location: (3,0)-(3,44))
        │   ├── name: :m
        │   ├── name_loc: (3,4)-(3,5) = "m"
        │   ├── receiver: ∅
        │   ├── parameters: ∅
        │   ├── body:
        │   │   @ StatementsNode (location: (3,7)-(3,39))
        │   │   └── body: (length: 1)
        │   │       └── @ SingletonClassNode (location: (3,7)-(3,39))
        │   │           ├── locals: []
        │   │           ├── class_keyword_loc: (3,7)-(3,12) = "class"
        │   │           ├── operator_loc: (3,13)-(3,15) = "<<"
        │   │           ├── expression:
        │   │           │   @ SelfNode (location: (3,16)-(3,20))
        │   │           ├── body:
        │   │           │   @ StatementsNode (location: (3,22)-(3,34))
        │   │           │   └── body: (length: 1)
        │   │           │       └── @ ClassNode (location: (3,22)-(3,34))
        │   │           │           ├── locals: []
        │   │           │           ├── class_keyword_loc: (3,22)-(3,27) = "class"
        │   │           │           ├── constant_path:
        │   │           │           │   @ ConstantReadNode (location: (3,28)-(3,29))
        │   │           │           │   └── name: :C
        │   │           │           ├── inheritance_operator_loc: ∅
        │   │           │           ├── superclass: ∅
        │   │           │           ├── body: ∅
        │   │           │           ├── end_keyword_loc: (3,31)-(3,34) = "end"
        │   │           │           └── name: :C
        │   │           └── end_keyword_loc: (3,36)-(3,39) = "end"
        │   ├── locals: []
        │   ├── def_keyword_loc: (3,0)-(3,3) = "def"
        │   ├── operator_loc: ∅
        │   ├── lparen_loc: ∅
        │   ├── rparen_loc: ∅
        │   ├── equal_loc: ∅
        │   └── end_keyword_loc: (3,41)-(3,44) = "end"
        └── @ DefNode (location: (5,0)-(5,45))
            ├── name: :m
            ├── name_loc: (5,4)-(5,5) = "m"
            ├── receiver: ∅
            ├── parameters: ∅
            ├── body:
            │   @ StatementsNode (location: (5,7)-(5,40))
            │   └── body: (length: 1)
            │       └── @ SingletonClassNode (location: (5,7)-(5,40))
            │           ├── locals: []
            │           ├── class_keyword_loc: (5,7)-(5,12) = "class"
            │           ├── operator_loc: (5,13)-(5,15) = "<<"
            │           ├── expression:
            │           │   @ SelfNode (location: (5,16)-(5,20))
            │           ├── body:
            │           │   @ StatementsNode (location: (5,22)-(5,35))
            │           │   └── body: (length: 1)
            │           │       └── @ ModuleNode (location: (5,22)-(5,35))
            │           │           ├── locals: []
            │           │           ├── module_keyword_loc: (5,22)-(5,28) = "module"
            │           │           ├── constant_path:
            │           │           │   @ ConstantReadNode (location: (5,29)-(5,30))
            │           │           │   └── name: :M
            │           │           ├── body: ∅
            │           │           ├── end_keyword_loc: (5,32)-(5,35) = "end"
            │           │           └── name: :M
            │           └── end_keyword_loc: (5,37)-(5,40) = "end"
            ├── locals: []
            ├── def_keyword_loc: (5,0)-(5,3) = "def"
            ├── operator_loc: ∅
            ├── lparen_loc: ∅
            ├── rparen_loc: ∅
            ├── equal_loc: ∅
            └── end_keyword_loc: (5,42)-(5,45) = "end"